The hypothesis to be tested in the current proposal is that killed S. aureus enhances the interaction of osteoblasts with biomaterials. The specific aims are the following: 1. Does UV-killed S. aureus enhance attachment of osteoblasts to thin films of titanium alloy? Polystyrene tissue culture dishes will be coated with titanium alloy Ti-6AI-4V (Ti) using thermal vapor evaporation. The Ti-coated culture dishes will be coated with fibronectin (Fn),-and incubated with UV-killed S. aureus strain UAMS-4. Culture dishes will then be rinsed to remove unattached bacteria, followed by culture of normal human osteoblasts in the coated dishes. Attachment of osteoblasts to Ti in the presence and absence of UV-killed S. aureus will be analyzed using phosphor-screen autoradiography. The strength of osteoblast attachment will be analyzed using micropipette aspiration techniques. Results will be compared to cultures of osteoblasts grown in dishes coated with Ti and Fn. 2. Does UV-killed S. aureus enhance spreading and proliferation of osteoblasts, and increase type I collagen synthesis on thin films of Ti alloy? Normal human osteoblasts will be cultured in Ti/Fn/S. aureus-coated dishes. Osteocalcin expression will be examined to assess spreading of the osteoblasts on the biomaterial. Amounts of alkaline phosphatase activity and 3H-thymidine incorporation will be assessed and used as indicators of osteoblast viability and proliferation, respectively. Type I collagen synthesis will be measured to assess production of bone matrix. Results will be compared to osteoblasts cultured in Ti/Fn-coated dishes. 3. Does UV-killed S. aureus enhance interfacial shear strength between bone and titanium implants in vivo? An in vivo model is proposed to address this aim. Titanium wire coated with Fn and UV-killed S. aureus will be inserted into the femoral canal of rats. Ti wire coated with Fn will be used as controls. Femurs will be harvested at different weeks following insertion. The implant interface will be examined using transmission electron microscopy and the interfacial shear strength assessed using a pull-out test.